figure;
[X, Y, Z] = peaks;
subplot(2, 2, 1);
contour(X, Y, Z, 20, 'LineWidth', 2);
subplot(2, 2, 2);
contour(X, Y, Z, '--', 'LineWidth', 2)
subplot(2, 2, 3);
v = [1, 1];
contour(X, Y, Z, v, 'LineWidth', 2);
x = -2:0.2:2;
y = -2:0.2:3;
[X, Y] = meshgrid(x, y);
Z = X.*exp(-X.^2-Y.^2);
subplot(2, 2, 4);
contour(X, Y, Z, 'ShowText','on', 'LineWidth', 2);
